There are numerous instances in which a tank or cylinder or other closed container is to be filled with a liquid, including a liquefied gas. One such instance involves small tanks or cylinders of liquid carbon dioxide (CO.sub.2) which are used to supply propellant gas to a paint ball gun. A "typical" tank or cylinder for this particular application holds approximately 9 ounces of liquid CO.sub.2.
One procedure now followed in filling a 9 ounce CO.sub.2 cylinder involves "syphoning" liquid CO.sub.2 from a larger supply tank into the cylinder to be filled. A filling procedure of this type is generally accomplished using the same valved opening into the cylinder which is used to supply gas to the operating elements of the gun. This requires, of course, that the cylinder be removed from the gun for filling.
More specifically, one prior art procedure for filling a small CO.sub.2 tank begins with the step of venting or emptying the tank of existing liquid and gas. The tank must typically be emptied unless the exact weight of the tank is known in advance. The tank is then chilled to reduce the volume of the remaining vapor in the tank. This allows liquid to flow into the tank without venting the existing vapor from the tank. Chilling of the tank may be accomplished by emptying a partially-filled tank. As the liquefied gas expands and escapes from the tank, the temperature of the tank drops significantly. Once the tank is emptied and cold, it is weighed. Following this step, the tank is connected to a supply tank to allow liquid CO.sub.2 to flow into the tank. The weight of the tank is monitored during filing to determine the amount of CO.sub.2 liquid placed in the tank. In some cases (e.g., if the tank is not chilled enough), the initial fill operation does not result in the required amount of liquid in the tank (for example, 9 ounces in tanks typically used with some paint ball guns). In that case, the tank is vented to further reduce the temperature, and the fill procedure is repeated.
Under "field" conditions a typical 9 ounce tank may take 2-3 minutes. A "full" tank is about 3/4 filled by volume to allow for some expansion of the gas to occur as the tank warms. Overfilling a tank can result in hazardous pressure buildups. To guard against over pressurization, rupture disks are typically used with prior art tanks.
One embodiment of the present invention includes a valve assembly which fits into the threaded opening of a cylinder, such as a standard 9 ounce CO.sub.2 cylinder. The valve assembly is used in conjunction with a nozzle assembly which is attached to a hose which, in turn, is connected to a source of supply of liquid CO.sub.2. The valve assembly and nozzle of the present invention allow for filling a warm cylinder with liquid CO.sub.2, filling a 9 ounce CO.sub.2 cylinder in a matter of seconds, rather than minutes, providing a visual indication that a tank has been properly filled to the appropriate level without requiring that the tank be weighed before or after the fill operation, and filling the cylinder through a separate fill inlet in the valve assembly which allows the cylinder to be filled while remaining mounted to the gun (or other appliance).
This embodiment of the valve and nozzle assembly of the present invention provides a separate, valved inlet which communicates with the interior of the tank or cylinder for receiving liquid into the tank. A vent opening, also communicating with the inside of the tank, allows vapor inside the tank to exit as liquid enters through the inlet. A shoulder or surface on the fill nozzle opens a vent on the valve assembly when the nozzle engages the valve assembly during the filling operation. A double-valve connection is provided between the supply tank and the tank or cylinder to be filled (i.e., one valve in the nozzle and one valve in the valve assembly).
Other advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.